AU
B16461A

This DTC indicates the measured resistance of the driver-side seat belt pretensioner ignition circuit falls below the SRS control module threshold (typically <1 — Seal U

Safety System

This DTC indicates the measured resistance of the driver-side seat belt pretensioner ignition circuit falls below the SRS control module threshold (typically <1.0Ω).

The seat belt pretensioner is a pyrotechnic actuator containing a resistance wire and ignition charge; normal resistance ranges from 2.0-5.0Ω.

Low resistance typically indicates a circuit short to ground, a wire-to-wire short, a partial short in the pretensioner internal resistance wire, or grounded connector pins.

This fault causes the SRS system to enter fail-safe mode.

During a collision, the pretensioner may fail to deploy and tighten the seat belt, or in extreme cases, poses a safety risk of unintended deployment.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1The seat slide rail pinches and chafes the pretensioner wiring harness (yellow harness) under the driver's seat, exposing the wire core and causing a short to ground.
  • 2Water ingress, oxidation, corrosion, or bent pins at the pretensioner connector (located at the B-pillar or under the seat) causing an abnormally low resistance connection.
  • 3Short circuit in the seat belt pretensioner body internal resistance wire (due to aging, moisture ingress, collision impact, or manufacturing defects)
  • 4SRS control module internal detection circuit fault or abnormal sampling resistor, causing a falsely low resistance reading.
  • 5Improper connection of the pretensioner connector during repair, or a detached wiring harness retaining clip causing the harness to rub against body metal and short circuit.
What To Do
  • 1
    Safety preparation: Disconnect the low-voltage battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor. Wear an anti-static wrist strap. Do not use a multimeter resistance setting to measure an energized airbag assembly.
  • 2
    Initial inspection: Remove the driver-side B-pillar lower trim panel and the seat. Visually inspect the dedicated yellow wiring harness for damage, pinching, or signs of water ingress. Focus on interference points between the seat slide rail travel path and the wiring harness.
  • 3
    Resistance measurement: Disconnect the pretensioner connector. Use a digital multimeter to measure the resistance between the two terminals of the pretensioner body (standard value: 2.0-5.0Ω). A reading of <1.0Ω indicates an internal short circuit in the pretensioner. Replace the seat belt assembly (including the pretensioner).
  • 4
    Circuit inspection: Measure resistance between the harness-side connector and body ground (should be >1MΩ). Check pins for bending, push-out, or oxidation. Repair wiring harness insulation or replace the connector if necessary.
  • 5
    System reset: After repair, reconnect all connectors and the battery. Use the BYD dedicated diagnostic tool (VDS2000/3000) to clear the fault code and perform an SRS system self-check. Slide the seat forward and backward to confirm the wiring harness has no interference.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro DM seat rail pinched wiring, causing pretensioner short circuit

✓
A 2018 Qin PRO DM had the dashboard airbag warning light permanently illuminated. Read DTC B16461A. Found the seat rails had pinched the yellow pre-tensioner wiring harness beneath the driver's seat over time, damaging the insulation and causing the exposed copper wires to short to ground. Measured pre-tensioner resistance at 0.3Ω (normal 2.5Ω). Repaired the damaged harness by re-soldering the broken wires and insulating with heat-shrink tubing. Rerouted the harness, added abrasion-resistant corrugated tubing and secured it with cable ties to avoid interference with the seat rails. Cleared the fault code and tested by repeatedly adjusting the seat position; the fault did not return.
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin PRO petrol: B-pillar connector water ingress and oxidation

✓
2019 Qin PRO (petrol variant). After driving in rain, the airbag warning light illuminated intermittently. The scanner showed intermittent DTC B16461A. Inspected the pretensioner connector inside the B-pillar trim and found the seal had deteriorated, allowing water ingress. The copper pins inside the connector had oxidised, turned black and developed green corrosion, causing a micro-short between terminals. The resistance fluctuated between 0.8 and 2.0 Ω. Repair: Replaced the pretensioner wiring harness connector (with waterproof seal), cleaned the pretensioner terminals, applied specialised conductive grease (anti-oxidation), and re-wrapped the harness with waterproof tape. Conducted a water spray test after repair; fault resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

Internal resistance wire in pretensioner aged and short-circuited

✓
2018 BYD Qin Pro DM, no accident history. The airbag warning light suddenly came on and stayed on, and the system stored DTC B16461A. Removed the driver's seat belt assembly, disconnected the pretensioner connector, and measured the unit's resistance: only 0.6 Ω. Diagnosed as a short circuit between layers of the pretensioner's internal resistance wire (likely caused by long‑term vibration or moisture ingress). Replaced the driver's side seat belt assembly (including pretensioner; part number must match the VIN). After replacement, the new part measured 2.4 Ω, meeting specification. Used a diagnostic tool to configure the SRS system by writing the new pretensioner serial number, cleared the fault codes, and the system passed the self‑test.
Other Seal U Fault Codes
B1108For the BYD Song MAX (2017–2019), DTC B1108 indicates a short circuit in the PM2.5 air quality detection module (dust sensor) or its wiring harness. The sensor uses laser scattering to detect in-cabin and outside PM2.5 concentrations and transmits data to the HVAC ECU via the LIN bus or an analog signal. Short circuit conditions include: 1) Sensor power supply wire (+5V/+12V) shorted to ground 2) Signal wire shorted to power or ground 3) Short circuit in the sensor's internal photoelectric detection circuit This fault prevents the automatic climate control from switching between fresh air and recirculation based on air quality. The system enters fail-safe mode (typically forced recirculation). Severe short-circuit current can destroy the HVAC ECU sampling circuit. The system classifies this as a Level 3 severe fault and restricts vehicle operation to prevent electrical fires or controller damage. For other BYD models (such as the Qin EV, E5, and Song DM), B1108 indicates a driver-side sunload sensor fault, reflecting differences in DTC definitions across models.B110811This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.B110913DTC B110913 indicates an open signal circuit for the PM2.5 rapid detector (in-cabin air quality sensor). This sensor typically mounts inside the air conditioning system intake duct. It monitors in-cabin PM2.5 concentration in real time and provides data to the automatic air conditioning system for intelligent control of the air purification function. The BYD diagnostic protocol uses sub-code '13' to specifically indicate an open signal circuit. Although this fault theoretically affects a comfort feature, BYD Qin series vehicles classify it as a Level 3 (severe) fault. This classification occurs because the air conditioning system interacts with the battery thermal management system (e.g., monitoring battery cooling intake air quality). The fault can disable the automatic air conditioning mode and prevent the air purification function from operating. In extreme cases, it affects the battery compartment intake air quality assessment, triggering the 'repair immediately' strategy.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.
Data confidence: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself. Sources: [1]